Determining an amount of air entering an engine, and in particular and amount of air in cylinders of the engine, is important for various aspects of engine control. For example, the fuel control and fuel delivery are typically coordinated based on a determination of air entering the engine to maintain a desired air to fuel ratio (air-fuel ratio).
It is known to use a lookup table of steady-state engine airflow versus engine speed and throttle to estimate engine airflow. This known estimate also used additional table adjustments for EGR, IMRC and VCT. Electronic throttle control system applications added a manifold filling model to these steady-state tables.
In some cases, the present inventors have recognized that it can be desirable to generate duplicate estimates of engine airflow. In some cases, these duplicate estimates can be generated from independent sensory information, or from common sensory information.
One disadvantage recognized by the present inventors relates to the manifold filling process. In particular, manifold filling refers to the filling/emptying dynamics of air storage in the intake manifold of the engine. In other words, airflow entering the manifold is not necessarily the same as the airflow exiting the manifold (entering the cylinders) due to the manifold volume. When duplicate estimates of air in the engine are generated using differing models (as differing sensor inputs are sometimes utilized), calculation errors between the duplicate estimates can be experienced.